Sunday, March 09, 2003

As a part of its continued interest in monarch butterflies, the Rio Bravo Nature Center sponsored its third eight-day trip to the Biosfera de la Mariposa Monarca in Michoacan, Mexico, at the end of February.

Scientists are marveling at the impressive comeback of the monarch butterflies, which once again are festooning the fir trees of central Mexico in a sea of orange and black, despite a deadly freeze last year that killed forty-seven percent of the population. Cold rains, followed by a six-inch snow, in the Preserve at El Rosario and Chincua in late January 2002 caused wide-spread alarm in the conservation world. The unprecedented numbers of deaths--some inaccurately estimated as many as 500 million butterflies perished, followed by severe drought conditions last summer in the northern central U. S--prompted concern that fewer numbers of the insects would arrive south of the border this year. The population this winter in the Transvolcanic Region of central Mexico appears to be about that of last year after the freeze—possibly as high as 100 million butterflies.

The continuing eruption of Popocateptl east of Mexico City and some 200 miles away had in no way disturbed the monarchs, since smoke was being blown in other directions.

The Nature Center group visited 4 preserves: El Rosario and Chincua, located in the state of Michoacan near Zitacuaro, and Capulin and Valle del Bravo sites in the state of Mexico. For the last two sites they were accompanied by Eligio Garcia Serrano, biologist formerly in charge of butterflies at the Preserve from 1991 to 2002.

On two occasions (at Capulin and Valle del Bravo), the group experienced rivers of monarchs flowing down off the mountains using the highway itself as a conduit to facilitate their flight. Biologist Garcia Serrano said that in his ten years collecting data and monitoring the monarchs, he had never before had the opportunity to observe such an amazing movement.

The flow at Capulin was 90' wide, and the group monitored the central flow in a rectangle 15' x 30', observing a continuous rate of 40-45 monarchs per second. This resulted in an extrapolation of 5,520 per minute; 331,200 per hour; and for 5 hours of the flow from 10 a. m. to 3 p.m., a population of 1,656,000 which were moving at 20 to 25 mph down an arroyo to the valley floor.

Ms. Carol Cullar, director of the Nature Center, said: “Numbers in no way enable me to describe what it was like to stand in the road with their orange fluttering filling the air, to feel the wind of their passage and, even in my hearing impaired state, to hear the passage of so many wings!”

When the group arrived at Valle del Bravo the following day, there was a similar, but much smaller population using the road as their departure flyway under the aegis of heavily armed state police, who enforced a slow crawl of the traffic through the fluttering ranks. Ms. Cullar said: “We rolled down our car windows and, sticking our arms out the window ‘flew along’ with the migration! There was something quite humorous about such delicate creatures being protected with sub-machine guns!”

Despite many reports to the contrary this past year, the monarchs are alive and well and headed toward Eagle Pass in two to three weeks. Their normal travel distances average about twenty-five miles per day. The monarchs are expected to spread out through Central Texas looking for milkweed on which to lay their eggs and will die soon after. This spring and summer their subsequent generations will reproduce and spread through much of the Eastern U. S. and Southern Canada before their grandchildren and great-grandchildren will once again make their way to the extinct volcanic slopes of Michoacan.

The Nature Center is sponsoring a research workshop this spring for teachers in the region who are interested in participating in a monarch monitoring/outdoor education project in conjunction with the University of Minnesota and the National Science Foundation. Teachers interested in participating and gaining CPE credit for their involvement should call the Center immediately.Anyone spotting monarchs in Maverick County this March and April is asked to call the Nature Center at 773-1836 to report their sightings.